Though obesity is the result of excessive caloric intake and inadequate physical activity, physiological, and metabolic factors also play a role. Positive correlation between changes in serum K concentration and changes in Resting Metabolic Rate (RMR) have been shown. Dietary potassium intake may possibly play a role in energy expenditure by stimulating the sodium pump (Na+-K+-ATPase) and thus elevating the RMR. Since this has an important implication in weight regulation we would like to investigate the effect of dietary potassium on RMR more extensively after a longer period of dietary K deprivation with other macro and micro nutrients kept constant. Fortunately, one of our current protocols in the Clinical Research Center, "Arginine Vasopressin, Potassium Excretion and Acid-Base Balance" is in the process of conducting a zero K diet. It compares a nine day normal K diet to 11 days of zero K and 11 days of high K with the same macro and micro- nutrients as well as fiber. Measurements of RMR will additionally provide insight into the relationship between dietary K and total energy expenditure.